There exist many applications for the use of electrical lamps on motor vehicles, such as automobiles and trucks. Large freight trucks, such as those having separable tractor and trailer combinations, utilize a particularly large number of lamps. Such trucks require lamps for sidemarking, braking, and turning indications, often numbering in the dozens of lamps.
Because these lamps are subject to failure from accident, corrosion caused by moisture from high pressure washing systems or other adverse chemical environments, vibration, mechanical failure, and the like, owners of such vehicles often find it necessary to replace the lamp units. Often, the lamp needs to be replaced while the truck is travelling away from its “home” repair facility. Each lamp manufacturer typically has its own proprietary connector system for connection of the lamp to the vehicle's wiring harness, thereby preventing interchangeability with other lamps available in the aftermarket for replacement in the event of a lamp or harness failure. This can result in downtime while waiting to find the same lamp or it may result in the mechanic cutting into the wiring harness in a makeshift way to connect a lamp not normally used on the vehicle. This type of repair compromises the wiring harness, often allowing corrosion to occur due to exposing the wiring to the environment. The trucking industry has therefore called for a standard system of connection that will allow any manufacturer's lamp to be replaced by any other manufacturer's lamp.
In response to this, the Society of Automotive Engineers (SAE) is proposing a new industry standard (SAE J2577) that will define rigid performance criteria for such lamps. SAE J2577 only specifies the configuration of the lamp side of the connection; manufacturers are free to design their own connectors to couple to the lamp. Among other things, SAE J2577 proposes to require a tactile indication that the connector is seated properly and a visual indication that the connector is properly oriented (i.e. a keyed connector).
Such functions are usually implemented by the use of hardshell technology where hard plastic male and female connectors mate to form the interface; however, their size and cost make them unattractive for most applications. Additionally, the necessary processes for incorporating hardshell connectors into a wiring harness require a great deal of process control to achieve the desired sealing and electrical characteristics. Internal seals are attached to each individual wire and internally between the male/female connector interface to form a watertight seal. This is an expensive approach because the number of components (four to six) and the additional labor required to assemble them to the wires and connector parts. Without tight manufacturing process controls, these connectors are prone to field failures. This same shortcoming also applies to the serviceability of the connection, since an improperly crimped or inserted terminal provides an entry point for moisture or other contaminants that may degrade the electrical performance of the circuit. Additionally, multiple connector types are required, depending upon the number of circuits utilized (e.g. two for marker functionality and three for marker and turn functionality); otherwise, a three-cavity connector must be used and the unused holes must be filled with a cavity plug. Failing to replace wire seals or cavity plugs during service is a major cause of premature connection failure.
Most of these sealing concerns are eliminated by overmolded connector solutions, in which a polyvinyl chloride (PVC) or another suitable compound is injection molded around one or more electrical terminals. In common practice, overmolded connectors are perceived as inferior due to their inability to properly mate or seal the lamp to the wiring harness due to their lack of operator feedback (visually or through tactile means) to communicate a solid connection. This can cause problems when the connectors are not fully seated, resulting in corrosion and premature failure of the lamp or harness. Most overmolded connectors also require the use of a dielectric compound to provide an additional barrier of protection against moisture, vibration and environmental contaminants.
There therefore exists a need for a lamp-to-harness connector that provides a tactile indication that it is seated properly and a visual indication that it is properly oriented, while avoiding many of the drawbacks of the hardshell connector technology. The present invention is directed toward meeting this need.